Why do we still confuse KW and KWH?

dmacarthur said:

So, having been guilty of mistakenly using these terms wrongly on this forum and having been savagely criticized for it, I say that we back off a bit. I know perfectly well the difference, I don't always use the correct terminology and I believe that context helps define the meaning. I know it ain't correct but ad hominem attacks don't help. We want to attract people to the EV world not repel them.

Click to expand...

I mirror this, as unpopular as it might be around here. I also know the difference but have been known to switch the two around when typing it out. When reading someone else's post I also let context tell me what they are asking, even though they may use the wrong term

I mirror this, as unpopular as it might be around here. I also know the difference but have been known to switch the two around when typing it out. When reading someone else's post I also let context tell me what they are asking, even though they may use the wrong term

Click to expand...

Having lived with batteries, solar panels and now a Leaf since the Arco "bronze" panels came around in the seventies maybe, the difference seems intuitive to me but my Dad was a physicist and a stickler for grammar...... maybe that is why I can't get the terms straight always! Rebel without a cause.....

I agree it's easy to get sloppy while typing and forget the h or mix-up kW with kWh by chance. But it is an important difference, much like the difference between amperes and volts, for instance, or more accurately miles vs miles-per-hour.

Asking lay people to know the differences may be a bridge too far but the concepts are important. It's too bad those terms are in widespread use instead of something like kiloWatts and MegaJoules.

martyscholes said:

So that it's noted, a coulomb is a large number (some 6.24 x 10^18) of electrons. One coulomb passing through one volt of electrical potential is a joule. A joule is a (small) unit of work. One joule per second is a watt. One thousand joules per second is a kilowatt. One thousand joules per second for an hour (3600 seconds) is a kilowatt hour, which is equivalent to 3.6 megajoules. It is a shame that KW and KWH are so similar sounding and in writing, but a KW is a thousand joules per second and a KHW is 3.6 megajoules (regardless of time).

What does it take to get this right? Am I just too pedantic?

Click to expand...

A MUCH simpler explanation. A non-engineer will be more confused after reading your post. Something like this would be good:

KW is a unit of power. It measures how fast energy is being consumed. A 100 watt light bulb consumes energy 4 times as fast as a 25 watt bulb.

KWH is a unit of energy. It measures how much energy is being consumed. A 100 watt bulb will consume 100 watt-hours of energy each hour, so it will take 10 hours to consume 1 KWH of energy.

To put this in LEAF terms, there are 3 more-or-less standard AC charging rates associated with the LEAF: 1.44 KW for 120 VAC charging, 3.3 KW or 6.6 KW for 240 VAC charging. These are the standard rates at which the LEAF on-board charger will consume energy when charging.

The amount of energy stored in the battery is measured in KWH, and it will take longer to acquire a given number of KWH at a lower KW charging rate.

Typos happen to everybody, but I'm no more likely to confuse kW and kWh that I am to confuse distance and speed.

That said, I find misspelled homonyms annoying. If the writer does not know the difference they should learn, and if they do know the difference they should take the time to get it right if they want to communicate effectively. Not doing so risks criticism or being ignored. kW and kWh kinda sorta falls into this category.